Elementary Statistics – Association Examples
(Note: In some of
these, and other real-world, examples, there is not necessarily one right
answer.)
- There is a strong positive
correlation between the life expectancy of a nation’s people and the
number of television sets per capita. The U.S.,
for example, is high in both variables, and Rwanda is low in both. Does TV
cause longer life? (If so, we could increase the life expectancy in Rwanda by
shipping a large number of TV sets to them.) Or is there another explanation
of this association?
- A researcher is interested in
whether breast-feeding helps increase a baby’s alertness. She finds a
group of women who breast-feed their babies and a group of women who do
not breast-feed, and she studies them. She finds a strong positive
association between breast feeding and baby alertness. Can she necessarily
conclude that breast-feeding causes a higher level of alertness? Are there
other possible explanations of this association?
- A 1975 survey by the National Center for Health Statistics showed
that the larger the hospital, the longer the average patient stays. The
average stay was 6.3 days in hospitals with less than 100 beds, and 8.8
days in hospitals with 500 or more beds. Comment on this association
(there may be multiple ways the association can be explained).